[TUHS] origins of void*
scj at yaccman.com
Mon Nov 6 02:58:01 AEST 2017
Ok, here's my memory of void *, blurred as it may be by time.
Void was put into C, but it was actually not necessary by itself --
the default return type was int, and if nobody was using the value
there was no particular reason to use it. So only those who were
practitioners of the strong-type religion tended to use it. A major
problem in making C strongly typed was deciding on a return type for
malloc. It had traditionally returned char *, but this would require
a cast to allow you to allocate things other than characters.
I was at a /usr/grp conference at the alcohol-fueled reception talking
to Charlie Roberts about the problems of making C more strongly
typed. The topic of malloc came up. All of a sudden Charlie got a
huge grin on his face and said "Hey! Why don't we have malloc return
void *". It took me a minute or two to even understand what void *
could possibly mean, but the idea was an instant winner. I seem to
recall it was done a week or two later. The idea may have simply
ready to be born and others may have had it as well, but this is what
I remember of it. And the experience sticks in my mind as being an
almost literal example of being "struck by an idea".
----- Original Message -----
From: "jnc at mercury.lcs.mit.edu (Noel" <Chiappa)>
To:<tuhs at minnie.tuhs.org>
Cc:<jnc at mercury.lcs.mit.edu>
Sent:Sun, 5 Nov 2017 10:43:06 -0500 (EST)
Subject:Re: [TUHS] origins of void*
> From: Clem Cole
> typing hard started to become more important in the kernel.
I can imagine! The V6 kernel had all sorts of, ah, 'unusual' typing -
learned to my cost when I did that hack version of 'splice()' (to
process in a pipline to drop out, and join the two pipes together
which I did in V6 (my familiar kernel haunt).
Since a lot of code does pointer math to generate wait 'channel'
when I naively (out of habit) tried to declare my pointers to be the
type, the math didn't work any more! ('ip', in this particular case,
declared to be an 'int *'.)
No doubt part of this was inherited from older versions (of the
C); the code was working, and there was no call to tweak it. The lack
casts/coercion in the V6 C compiler may have been an issue, too - I
had to do
some equally odd things to make my splice() code work!
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